We will investigate the hypothesis that amino acid transmembrane transport relative to the rate of protein breakdown is central in mediating changes in muscle protein metabolism. We will determine the effect of acute (8hr.) and four days of cortisol treatment (6mg/m2/hr) on transmembrane amino acid transport. We will subsequently determine the effect of anabolic factors (insulin and amino acid) transport and muscle protein metabolism during cortisol excess. Stable isotope tracers will be utilized to measure these effects in normal volunteers.